The problems solved by the present invention were discussed at length in the prior patent application cited above, and the background section of that application will therefore be repeated here.
Support pads are used in a wide variety of applications to provide cushioned support to an injured or otherwise sensitive bodily appendage. Such pads have the dual purpose of (1) providing orthopaedic support to the appendage and (2) protecting the appendage from further injury or damage resulting from contact with a foreign object or hard surface.
One common use of a support pad is as a cushioned foot sole in specialized footwear such as soft boots or patient walkers. These devices generally employ some type of soft, resilient material, such as foam, to provide cushioned support of a sensitive or damaged foot.
A particular problem arises when it becomes necessary to provide uneven support across the outer surface of an appendage. For example, an ulcerated appendage, often found in diabetic patients, requires pressure relief to the ulcerated area to allow healing. In this instance, it is desirable to have a pad which will apply cushioned support to the appendage, while refraining from supporting the afflicted area. For diabetic patients, the feet are commonly beset with such ulcerations, and it is therefore desirable to provide a cushioned support sole for a shoe or walker which is capable of providing specific zones of pressure relief.
Other approaches have addressed the problem of providing cushioned foot support. U.S. Pat. No. 2,598,217 (Bronson), issued May 27, 1952, discloses as invalid's boot with a thick insole. However, these approaches require replacement of the sole for each new patient, or for each new area of the original patient's foot which must be relieved.
Andrews U.S. Pat. No. 4,793,078 discloses a footwear insole with a molded arch support. The insole has either three indentations or a single banana-shaped indentation arranged in an arc behind the toes, and another indentation at the heel. A user may adhesively fix pad inserts into one or more of the indentations to provide support to the foot. The user omits inserts from selected indentations to relieve pressure on certain area of the foot.
Unfortunately, a number of problems arise when diabetes patients, who are prone to severe foot ulcers, attempt to use the Andrews device. Before discussing these deficiencies, however, it is useful to review the foot problem that many diabetes patients face. It is well known that diabetes patients are prone to foot ulcers. In fact, lesions of the foot are responsible for more than one-fifth of the hospitalizations of diabetic patients. More than 40% of the lower extremity amputations in the United States are performed on diabetic patients who have poor circulation in the lower limb. With reduced sensation in the foot, the patient is unlikely to feel discomfort when the skin is subject to shear forces during walking, and consequently he or she does not properly adjust his or her gait. Lesions are formed or are made worse.
Diabetes patients also experience other extreme difficulties with their feet. Diabetic patients often undergo an unfortunate evolutionary pattern of anatomical deterioration. Initially, the foot will have a normal appearance and will only have vascular or neuro-vascular deficiencies. However, the bone structure can quickly deteriorate. Charcot joints can form, and the foot becomes drastically deformed. From then on, the areas of the foot that can bear weight are abnormal, their locations are unpredictable, and custom foot accommodations will be required for the remainder of the person's ambulatory life.
The Andrews device does little to overcome these problems. Foot ulcers and bone deterioration can occur anywhere on the foot, yet Andrews provides only a few pads in very specific locations. The Andrews fixed-location pad arrangement cannot provide pressure relief to damaged areas of the foot that are located anywhere except the four specific pad locations. This makes Andrews inadequate for the majority of diabetes patients with damaged feet.
An additional drawback of the Andrews pad is that it lacks means to reduce shear forces on the skin of the foot that arise as the patient walks along. Such shear forces can further damage existing ulcers, or create new ulcers. This is particularly true where the patient walks for any distance.
Other deficiencies of Andrews are apparent. As shown in Andrews FIG. 1, the Andrews sole is limited to either a left or right foot-only sole. The same Andrews sole cannot be used on either foot because sole support 16 is built into the shoe.
U.S. Pat. No. 3,760,056 (Rudy), teaches a method for conforming a ski boot to the foot of the wearer by heating an inflatable bladder, distending it to the desired shape, and then cooling and deflating the bladder. The bladder can be subsequently be re-inflated to fit the wearer's foot. This method requires a mechanism for heating, which may be inconvenient or impractical when applied to a comfortable sole. In the method disclosed, the inflatable bladder was placed over the foot to contact opposing sides, rather than underneath it as a support. Moreover, the elastomeric materials described in the Rudy patent typically may not provide the requisite comfort and cushioning generally required in a healing device.
A further method of providing support to an injured foot is disclosed in U.S. Pat. No. 5,078,128 (Grim, et al.) in which a removable leg walker includes a plurality of inflatable and adjustable bladder members in order to provide variable amounts of pressure to an affected limb as leg swelling increases or decreases. However, the bladder members of the Grim device do not retain their shape except as restrained by the surface of the appendage itself and thus do not provide the desired semi-permanent areas of relief to an injured appendage.
Incidentally, the above-cited U.S. patent application Ser. No. 07/965,750 discloses arrangements which provide relief using a pad of particulate material which is vacuum formed to the desired configuration.
From an overall standpoint, a principal object of the present invention is to provide a comfortable cushioned sole which may be conveniently modified to provide pressure relief to specific areas of the wearer's foot.
Another important object of the invention is to furnish a device which may be reused to provide relief to different areas of the patient's foot, or which may be used by other patients.
A further object is to provide a method for comforting a cushioned sole to the foot of a particular wearer, and of later reforming or returning the sole to its original shape.